Enumeration of DNA molecules bound to a nanomechanical oscillator

Resonant nanoelectromechanical systems (NEMS) are being actively investigated as sensitive mass detectors for applications such as chemical and biological sensing. We demonstrate that highly uniform arrays of nanomechanical resonators can be used to detect the binding of individual DNA molecules through resonant frequency shifts resulting from the added mass of bound analyte. Localized binding sites created with gold nanodots create a calibrated response with sufficient sensitivity and accuracy to count small numbers of bound molecules. The amount of nonspecifically bound material from solution, a fundamental issue in any ultra-sensitive assay, was measured to be less than the mass of one DNA molecule, allowing us to detect a single 1587 bp DNA molecule.     

Synergistic effects of hollow structure and surface fluorination on the photocatalytic activity of titania

To study the synergistic effects of hollow structure and surface fluorination on the photoactivity of TiO₂, TiO₂ hollow microspheres were synthesized by a hydrolysis–precipitate method using sulfonated polystyrene (PS) as templates and tetrabutylorthotitanate (TBOT) as precursor, and then calcined at 500 °C for 2 h. The calcined samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N₂ sorption. Photocatalytic activity was evaluated using reactive brilliant red X3B, an anionic organic dye, as a model pollutant in water. The results show that the photocatalytic activity of TiO₂ hollow microspheres is significantly higher than that of TiO₂ nanoparticles prepared in the same experimental conditions. At pH 7 and 3, the apparent rate constants of the former exceed that of the latter by a factor of 3.38 and 3.15, respectively. After surface fluorination at pH 3, the photoactivity of hollow microspheres and nanoparticles further increases for another 1.61 and 2.19 times, respectively. The synergistic effect of surface fluorination and hollow structure can also be used to prepare other highly efficient photocatalyst.     

Effects of dimensionality and crystal structure on bound states of point defects in quantum solids

The effects of dimensionality and crystal structure on the bound states of point defects in quantum crystals are investigated. It is shown that tightly bound states tunnel slowly in some lattices (e.g., bcc) while they tunnel quickly through other lattices (e.g., hcp). Explicit band calculations are made for ( ³ He) ₂ impurity molecules in solid host ⁴ He crystals. These illustrate the qualitative differences present in various molecular tunneling modes.     

热处理对贮氢合金结构和特性影响的研究

主要针对采用双辊快淬法制备获取的纳米晶稀土贮氢合金热处理前后相结构和PCT特性的变化进行了研究.X射线衍射、SEM、PCT测试结果表明,经热处理后合金的晶粒尺寸仍保持为纳米晶,从而有利于大电流充放电;合金的晶格缺陷减少,吸放氢平台斜率降低,磁滞减少,成分均匀性明显提高,这些都有利于提高合金的充放电稳定性.     

Environmetric strategies to classify, interpret and model risk assessment and quality of environmental systems

The present paper deals with the application of some environmetric approaches such as cluster analysis, projection pursuit, Kohonen maps, neuron gas, principal components analysis, chemical mass balance modelling, multiple regression on principal components, and time-series analysis in environmental data mining. Several ecologically important objects including marine sediments, wet and dry atmospheric precipitation are treated in order to obtain relevant information about monitoring data set structure and relationships. Multivariate statistical models are offered, which could help in decision making and problem solution of the local environment. In this way the case studies are a contribution to the idea of the increasing role of the environmetrics in the concept of sustainable development.     

圆柱壳体与法兰对接环形焊缝的焊接变形规律研究

利用模型试验研究了大型圆柱形体与法兰对接环形焊接的变形。结果表明，圆柱菜壳体与法兰对接环形焊缝将引起壳体的径向变形法兰平面度的变化；实际真空容器壳体的径向变形与模型试验壳体的径向变形相近，而环缝引起法兰平面外倾的斜率比模型试验法半平上倾的率小一个数量级。角变形对法兰平大幅度没有明显影响。     

Simulation study on discrete charge effects of SiNW biosensors according to bound target position using a 3D TCAD simulator

We introduce a simulation method for the biosensor environment which treats the semiconductor and the electrolyte region together, using the well-established semiconductor 3D TCAD simulator tool. Using this simulation method, we conduct electrostatic simulations of SiNW biosensors with a more realistic target charge model where the target is described as a charged cube, randomly located across the nanowire surface, and analyze the Coulomb effect on the SiNW FET according to the position and distribution of the target charges. The simulation results show the considerable variation in the SiNW current according to the bound target positions, and also the dependence of conductance modulation on the polarity of target charges. This simulation method and the results can be utilized for analysis of the properties and behavior of the biosensor device, such as the sensing limit or the sensing resolution.     

Synergetic effects of nanoporous support and urea on enzyme activity

We report synergetic effects of functionalized mesoporous silica (FMS) and urea to promote favorable protein conformational changes. The specific activity of glucose isomerase (GI) entrapped in FMS in the presence of urea was approximately double that of GI in solution in the absence of urea. Rather than losing all activity in a denaturing solution of 8.0 M urea, the specific activity of GI entrapped in FMS remained higher than the highest specific activity of GI free in solution.     

Study on the structure and antibacterial activity of silver-carried zirconium phosphate

The structure and antibacterial activity of silver-carried zirconium phosphate (AgZrP) were investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and viable cell counting method. There existed the exchange of sodium ions with silver ions in carrier, and the silver in AgZrP was in ionic state. Moreover, no significant changes in crystal structure of carrier were found by the exchange of silver ions except for its crystal space distance and crystallinity. The antibacterial tests showed that 100 mg l^− 1 of AgZrP possessed high antibacterial activity and was capable of killing all the Escherichia coli (E. coli) and more than 99.9% of the Staphylococci aureus (S. aureus) within 8.0 h of contact.     

Modelling the effect of structure and base sequence on DNA molecular electronics

DNA is a material that has the potential to be used in nanoelectronic devices as an active component. However, the electronic properties of DNA responsible for its conducting behaviour remain controversial. Here we use a self-consistent quantum molecular dynamics method to study the effect of DNA structure and base sequence on the energy involved when electrons are added or removed from isolated molecules and the transfer of the injected charge along the molecular axis when an electric field is applied. Our results show that the addition or removal of an electron from DNA molecules is most exothermic for poly(dC)-poly(dG) in its B-form and poly(dA)-poly(dT) in its A-form, and least exothermic in its Z-form. Additionally, when an electric field is applied to a charged DNA molecule along its axis, there is electron transfer through the molecule, regardless of the number and sign of the injected charge, the molecular structure and the base sequence. Results from these simulations provide useful information that is hard to obtain from experiments and needs to be considered for further modelling aiming to improve charge transport efficiency in nanoelectronic devices based on DNA.     

Support effects on hydrotreating activity of NiMo catalysts

The effect of the gamma alumina particle size on the catalytic activity of NiMoS_x catalysts prepared by precipitation method of aluminum acetate at pH = 10 was studied. The structural characterization of the supports was measured by using XRD, pyridine FTIR–TPD and nitrogen physisorption. NiMo catalysts were characterized during the preparation steps (annealing and sulfidation) using transmission electron microscopy (TEM). Hydrogen TPR studies of the NiMo catalysts were also carried out in order to correlate their hydrogenating properties and their catalytic functionality. Catalytic tests were carried out in a pilot plant at 613, 633 and 653 K temperatures. The results showed that the rate constants of hydrodesulfurization (HDS), hydrodenitrogenation (HDN) and hydrodearomatizing (HDA) at 613–653 K decreased in the following order: A > B > C corresponding to the increase of NiMoS particle size associated to these catalysts.     

The Effect of Three-Dimensional Deformations on Local Heat Transfer to a Nonuniformly Heated Falling Film of Liquid

An experimental investigation is performed of heat transfer under conditions of flow of a water film on a vertical surface with a heater 150×150 mm in size in the range of the Reynolds number values from 1 to 45. A map of modes of flow of the liquid film is plotted, and regions of heat transfer are identified. Data are obtained on the longitudinal coordinate dependence of the heater wall temperature and of the local heat flux on the symmetry axis of the heater. Local coefficients of heat transfer are measured. The experimental data are compared with the results of numerical calculations for a smooth film. The effect of the forming of jet flows on heat transfer to the liquid film is analyzed.     

纳米氧化锌中空柱的制备及其光催化性能的研究

以醋酸锌和氨水为原料,超声法制备出氧化锌中空柱,采用扫描电镜(SEM)、X射线衍射(XRD)、Uv-vis漫反射对纳米ZnO的形貌、结构进行了表征,以有机染料亚甲基蓝溶液为光催化反应模型降解物,考察纳米ZnO的光催化性能。结果表明:制备出的纳米氧化锌呈中空的柱形,长约2～3μm,直径约300nm,壁厚约40nm,结晶良好。当加入纳米ZnO为0.4g/L,光降解时间为75min,对亚甲基蓝溶液的降解率可达到99.08%。     

Semi-solid thixo casting structure of aluminum alloy and relevant assistant analysis with the help of computer simulation

The relationship between structure morphology of semi-solid aluminum alloy die-casting sample and filling condition was studied. By systematical structure analysis and computer simulation of the filling process, the quantitative relationship between microscopic morphology (such as solid fraction, grain size and shape) and formation state was studied. The results showed that the billet microstructure must have fine and round grains for the die-casting of complex shapes. It is necessary to optimize injection speeds to escape the non-uniform distribution of the solid fraction in complex and changeable mold cavity.     

Semi-solid thixo casting structure of aluminum alloy and relevant assistant analysis with the help of computer simulation

The relationship between structure morphology of semi-solid aluminum alloy die-casting sample and filling condition was studied. By systematical structure analysis and computer simulation of the filling process, the quantitative relationship between microscopic morphology (such as solid fraction, grain size and shape) and formation state was studied. The results showed that the billet microstructure must have fine and round grains for the die-casting of complex shapes. It is necessary to optimize injection speeds to escape the non-uniform distribution of the solid fraction in complex and changeable mold cavity.     

Annealing effects on the photocatalytic activity of ZnO nanoparticles

This paper describes the development of ZnO nanoparticles by a chemical method, to test them in the photocatalysis of the degradation of textile dyes, using Rhodamine B (RhB) as a probe reaction. The samples were submitted to different heat treatments in order to observe the annealing effects on the photocatalytical properties, surface decontamination and the consequent particle change, in terms of crystallinity. The as-prepared samples (ZOA) correspond to a metastable phase (oxy or hydroxy zinc acetate) and post annealing leads to ZnO crystallization. In spite of the XRD patterns showing only the ZnO phase for heat treatment at 100 degrees C, FTIR data show that carboxylate groups remains attached to the ZnO surface up to 300 degrees C. Up to 300 degrees C the presence of these carboxylate groups, provided by the synthesis method, showed to be more relevant to photoactivity than the specific surface area. At higher temperatures, crystallinity becomes the dominant factor and an increasing of crystallinity favors the photoactivity.     

Substrate effects on the structure and optical properties of GaN epitaxial films

The phase composition and luminescent properties of GaN films grown by molecular beam epitaxy on (0001) sapphire and 6H-SiC substrates were studied. The films grown on SiC were found to consist only of the hexagonal phase and contain a lower concentration of impurities. Grains of cubic GaN, as well as donor and acceptor impurities, were found in the GaN film grown on sapphire. The formation of impurity centers is caused by the diffusion of oxygen and aluminum from the sapphire substrate during crystal growth.